Field of the Invention
The present invention relates to a phosphor with a preferred orientation, a fabricating method thereof, and a light-emitting element package structure employing the same, and in particular it relates to a phosphor with a preferred orientation, which is capable of increasing the color rendering index, a fabricating method thereof, and a light-emitting element package structure employing the same.
Description of the Related Art
In recent years, energy-saving and environmental protection concepts have been a major concern. As new lighting sources, light-emitting diodes (LEDs) can solve problems that cannot be conquered by traditional incandescent lamps or fluorescent lamps. Also, LEDs meet the requirements of having low power consumption and environmental protection. Therefore, issues such as exploiting new energies and increasing energy efficiency have attracted the public's attention. Color LEDs have been used widely in colored lighting, displays, entertainments, and so on. The development of the electronic display industry has been the most rapid. It is believed that LEDs will play an important role in photoelectric element applications in the future.
So far, the development of white light-emitting diodes (WLEDs) is the main developmental direction of LEDs in global. WLEDs have advantages such as small size, low heat radiation, long life, low power consumption, and vibration resistance. WLEDs solve the problems that cannot be conquered by traditional lamps. As traditional energy-consuming and polluting incandescent lamps have been eliminated or prohibited around the world, such as in the European Union, Australia, and America, the uses of LEDs have developed from functional uses such as street lighting, traffic signals, or special household electrical appliances to general use such as household lighting, large displays, automotive lighting, indoor lighting, or the backlight modules of electronic products. As a result, the market penetration rate of LEDs continuously increases at a rate of 10-15% every year. The result further reveals the developmental value of WLEDs in the field of lighting for a new generation.
Many countries are actively involved in the LED industry. So far, it is well known that Nichia (Japan) employs a technique that excites yellow light-emitting phosphor in blue LED chips to improve the luminous efficiency of white light, and with a low manufacturing cost. Also, Cree (America) uses UV to excite phosphors to produce white light. In addition, Siemens and Philips (Europe) use a method of exciting terbium aluminum garnet (TAG; Tb3Al5O12) in UV chips to produce WLEDs with high luminous efficiency.
One of the most common WLEDs used in the industry include blue LED chips accompanied by YAG phosphor (Y3Al5O12:Ce; Yttrium aluminum garnet). However, in order to remedy the red light spectrum which YAG phosphor (Y3Al5O12:Ce; Yttrium aluminum garnet) lacks, the process for the red light-emitting phosphor-added WLEDs has become a new issue. So far, there is lots of information about the synthesis and applications of the red light-emitting phosphor. For example, it is known that A2[MF6]:Mn4+ (wherein A is Li, Na, K, Rb, Cs, NH4; and M is Ge, Si, Sn, Ti, Zr) fluorides may serve as a red light-emitting phosphor for LEDs. In addition, Xueyuan Chen et al. have also tried to improve the synthesis condition, luminous efficiency, and heat resistance of their published K2TiF6:Mn4+.
Therefore, for the current progress of LEDs to continue, it is important to provide a red light-emitting phosphor capable of increasing the color rendering index for WLEDs, and a fabricating method thereof.